Fertility of irrigated lands in the south forest-steppe of the Omsk region

Abstract

Unsustainable irrigation of chernozems can lead to secondary salinization and other negative consequences. The purpose of the research was to assess the fertility and hydrochemical composition of meadow-chernozem soil of the forest-steppe of Western Siberia under conditions of prolonged irrigation. The surveys were carried out in the fields of the agricultural production cooperative (APC) “Pushkinsky” and Federal State Unitary Enterprise (FSUE) “Omskoye”; cultivation technology – adaptive system of irrigated agriculture. The studies were conducted in 2015–2020 on the Pushkin irrigation system. The object of the research – irrigated meadow-chernozem heavy loamy soil. The methods of route field research and laboratory analyzes were used. The results obtained were compared with the baseline values (1978). With long-term irrigation and intensive agricultural use, the fertility indicators of meadow-chernozem soil did not significantly deteriorate. The arable horizons have a neutral and close to neutral reaction (pH 5.8–6.2), average humus content (5.9–7.2%). The supply of nitrate nitrogen, as a rule, remained at a low and medium level (6.0–14.7 mg/kg) due to the high removal by vegetative crops and the absence of fallow fields in the structure of irrigated arable land. Long-term systematic application of phosphorus-containing fertilizers and creation of a positive P balance led to the improvement of soil phosphate status (99–177 mg/kg). The content of exchangeable potassium remains high (144–353 mg/kg) and is stable over time, which is a feature of chernozems with a heavy particle size distribution. The content of mobile forms of lead, zinc and cadmium does not exceed approximate permissible concentrations in the soil. When analyzing the cation-anionic composition of the water extract of the soil profile of FSUE “Omskoe”, a weak salinity of the chloride type was revealed in the 0.6-1.4 m layer; of the sulfate-chloride type – in the 1.4-1.8 m layer. In the future, it may lead to secondary salinization and serve as a limiting factor for high yields. The absorbing complex of meadow-chernozem soil in the southern forest-steppe is highly saturated with bases. Sodium concentration is minimal; calcium and magnesium cations prevail. The groundwater samples are moderately fresh and of good quality. Among the anions, HCО3- prevails, among the cations – Mg2+ and Ca2+, which indicates the need to control the groundwater level to maintain a favorable ecological state of meadow-chernozem soil.

Magnesium in Soils of Agricultural Landscapes of Western Siberia

“…The humus content (determined by Tyurin's method) in the Gleyic Chernozems soil changed insignificantly as a result of long-term cultivation. This is associated with a significant proportion of perennial grasses in crop rotations and, accordingly, a large amount of root and crop residues Magnesium in Soils of Agricultural Landscapes of Western Siberia entering the soil (W eißhuhn et al, 2017;Boiko, 2019;Levin et al, 2021). The pH value of the soil under study increased slightly during the experiment -by 0.2-0.3 units.…”

“…Long-term extensive agricultural use of Gleyic Chernozems soil did not affect the soil level of exchangeable Mg (Table 3). Probably, the predominant cultivation of grasses weakened the processes of infiltration and leaching and the mineralization in the upper soil layers of a large number of plant residues (Boiko, 2019) contributed to the compensation of the removal of the element with the harvest. However, judging by the slight decrease in the content of the easily exchangeable fraction of magnesium, it is obvious that, despite the external invariability of the pool of intracellularly absorbed cations, the soil's ability to desorb magnesium ions into the soil solution to a certain extent decreased.…”